Propriedades físicas e químicas de solo alterado com aplicação de adubos orgânicos

Abstract

Reusing organic fertilizers is essential for agricultural sustainability. Still, it is crucial to consider the type of soil and quantities of fertilizers to be applied to avoid problems such as salinization, alkalinization, and clay dispersion, which can damage crop yields and degrade the soil. The aim was to assess clay dispersion and its relationship with Na+ , Ca+2 content, and soil pH values after seven years of using poultry litter and swine manure biofertilizer (SMB) in a clayey latosol under no-till farming. To this end, in 2021 and 2022, during the winter harvest, analyses were carried out in an experiment that had been implemented since 2015 under no-till farming and with applications of organic fertilizers during the summer and winter harvests at the Paraná Rural Development Institute (IDR-PR), in Santa Tereza do Oeste-PR. The work was divided in relation to the source of fertilizer used, one with poultry litter and the other with SMB. The doses applied were calculated based on the amount of nitrogen required by the triticale (72 kg ha-1 ) for mineral fertilization and then doubled and tripled. The treatments included Control, Chemical, and Organic fertilizer (poultry litter 3.6, 7.2, and 10.8 Mg ha-1 or SMB 60, 120, and 180 m3 ha-1 ). The effects of poultry litter and SMB on the soil were analyzed, associating clay dispersion with the soil's Na+ , Ca+2, pH, and organic matter (OM) levels in the 0-10 cm layer. Physical attributes of the soil were also assessed, such as total clay, total porosity, macroporosity, microporosity, and hydraulic conductivity of the saturated soil in the 0-10, 10- 20, and 20-30 cm depth layers. PH, electrical conductivity, and sodium saturation index were analyzed to check for soil salinization. The results were submitted for analysis of variance, and the means of the treatments were compared using the Tukey test at 5%. The correlation between the variables was assessed using Pearson's correlation analysis; the variation in soil properties was analyzed using principal component analysis (PCA). The work hypothesized that the cementing action of OM from poultry litter or SMB could mitigate any effects of dispersion of clay minerals due to salinization or alkalinization. The results indicated that poultry litter increased Na+ and associated pH and Ca+2 levels and contributed to increased clay dispersion at doses of 7.2 and 10.8 Mg ha-1 . Therefore, the hypothesis that organic matter from poultry litter could reduce clay dispersion or increase the stabilization of soil aggregates was refuted. PCA explained 77.88% of the variation and revealed that clay dispersion correlated with Na+ , pH, Ca+2, and MO, suggesting caution when using poultry litter in Latosols. When applying poultry litter, doses higher than 7.2 Mg ha-1 potentially harm the soil. Therefore, it is recommended to use poultry litter in doses of 3.6 Mg ha-1 to increase grain productivity and replace mineral fertilization. Concerning the use of SMB, there was an increase in MO and the stability of soil aggregates, which reflected higher geometric mean diameter (GMD) values with doses of 60 and 180 m3 ha-1 . In addition, the high pH and MO levels in the soil favored the predominance of negative charges and led to the dispersion of clay minerals. PCA explained 79.6% of the total variation and confirmed the positive effect of SMB on soil properties, especially on MO and GMD. Thus, the SMB dose of 180 m3 ha-1 may benefit Latosols. These results provide insights into the possible risks and benefits of using organic fertilizers in agriculture, specifically in terms of clay dispersion and soil structure.